With the increasing use of portable device such as smart phones, tablet PCs, laptop computers, portable multimedia players and the like, the battery available time of the portable devicees as well as their performance ability has been emerging as a major issue lately. In other words, since the portable device has a difficulty in being equipped with a large amount of batteries due to their portability, it has become required to develop a technique for extending the battery available time of the portable device.
There has suggested a conventional method for extending the battery available time by using the dynamic voltage scaling (DVS). The DVS is a method of varying by the software control an operation frequency and a supply voltage supplied to the processor equipped in a portable device.
However, the conventional method using the DVS is disadvantageous in that it is possible to use a portable device equipped with a processor supporting the DVS only and it is necessary to include additional units such as a DC-DC converter, a frequency synthesizer and the like, causing additional power consumption and time delay. Further, it is not an efficient work to reduce the voltage supplied to the processor even in consideration of a battery discharge structure.